Electrochemical determination of trace amounts of environmentally important dyes

A number of dyes exhibit genotoxic or ecotoxic properties leading to the need for sensitive and selective methods for their determination. Because of the easy reducibility of dyes, modern polarographic and voltammetric methods (differential pulse polarography on classical dropping mercury electrode, differential pulse voltammetry on hanging mercury drop electrode or adsorptive stripping voltammetry) are suitable for the determination of trace amounts of these substances in the general environment in the vicinity of production plants. The scope and limitations of these methods is reviewed and optimum conditions for recently developed methods are summarized. It is shown that the sensitivity of newly developed polarographic and voltammetric methods is sufficient even for the most demanding applications and their selectivity can be increased by their combination with preliminary separation using thin layer chromatography or liquid extraction.     

Kinetic-spectrofluorimetric determination of trace amounts of iridium

A simple and sensitive kinetic-spectrofluorimetric method is described for the determination of iridium(IV) and the possible mechanism of catalytic reaction is proposed. The method is based on the fluorescent quenching reaction of salicylaldehyde p-nitro-benzoylhydrazone (SAP-NBH) with potassium periodate, inhibited by Ir(IV) in a water-ethanol (7.3+2.7, v/v) medium at pH 10.70 and 55 degrees C. Cetyltrimethyl ammonium bromide sensitized the determination obviously. SAP-NBH was newly synthesized and its ionization constants were established spectrophotometrically. The reaction was monitored by measuring the change rate of fluorescence (lambda ex/em=252/310 nm) after a fixed time of 5 min. The proposed method allowed the determination of iridium in the range of 0.11-18 ng ml(-1) with a RSD of 2.5% at a concentration of 10 ng ml(-1) and the detection limit was down to 0.09 ng ml(-1). The method was found to be relatively selective and was applied successfully to determine iridium in synthetic mixtures and mineral sample with the results consistent well with the ref. values.     

Polarographic determination of trace amounts of thorium

A sensitive linear-sweep polarographic method for the determination of thorium is described. It is based on the thorium complex with Xylidyl Blue I (XBI) in a medium containing ethylenediamine, 1,10-phenanthroline, oxalic acid and ninhydrin, at pH 10.5-11.5. The complex has been proved to be Th(XBI)(2), with log beta' = 9.6. The method can be used to determine trace amounts of thorium over the range 3.5 x 10(-8)-3 x 10(-6)M. The detection limit is 1 x 10(-8)M. A solvent extraction procedure is necessary to eliminate interference from several cations. The method has been applied to determination of traces of thorium in minerals, with good results.     

Catalytic determination of trace amounts of vanadium

Summary Some new oxidation reactions of arylamines catalysed by traces of vanadium have been found. It is shown that phenolic compounds have a favourable effect on these processes. Investigations were carried out on the oxidation ofp-phenetidine citrate by potassium chlorate in the presence of vanadium as catalyst and of phenol as activator. A colorimetric method for the determination of 0.1–8g of vanadium, based on this process, is reported.

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Zusammenfassung Einige neue, durch Vanadiumspuren katalysierte Oxydationsreaktionen von Arylaminen wurden gefunden. Phenolische Verbindungen haben auf diese Reaktionen erheblichen Einfluß. Die Oxydation vonp-Phenetidincitrat durch Kaliumchlorat bei Gegenwart von Vanadium als Katalysator und Phenol als Aktivator wurde untersucht. Eine kolorimetrische Methode zur Bestimmung von 0,1 bis 8g. Vanadium wurde auf dieser Grundlage ausgearbeitet.

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Résumé On a trouvé quelques nouvelles réactions d'oxydation des arylamines catalysées par des traces de vanadium. On montre que les composés phénoliques ont un effet favorable sur ces processus. On a effectué des recherches sur l'oxydation du citrate dep-phénétidine par le chlorate de potassium en présence de vanadium comme catalyseur et de phénol comme activateur. On présente une méthode colorimétrique pour le dosage de 0,1 á 8g de vanadium, fondée sur_ce procédé.

     

Spectrofluorimetric determination of trace amounts of thorium

A spectrofluorimetric method, based on the formation of a fluorescent complex with salicyladehyde carbohydrazone, is optimized for the determination of thorium (20–800 μg l^?1) at “pH” 1.3–1.7. The relative standard deviation is 2.7% for 100 μg Th l^?1. The method is applied to synthetic mixtures containing various amounts of thorium and to the determination of thorium in monazite samples.     

Kinetic-spectrophotometric determination of trace amounts of vanadium

A simple and sensitive kinetic-spectrophotometric method is described for the determination of vanadium and the possible mechanism of catalytic reaction is proposed. The method is based on the vanadium(V)-catalyzed oxidation of 1,8-diaminonaphthalene (DNA) by potassium bromate (Tiron as activator) at pH 3.8 and 40 degrees C. The reaction was monitored spectrophotometrically by measuring the increase in absorbance of oxidation products at 505 nm after a fixed time (6 min). The proposed method allowed the determination of vanadium in the range 0.025-15 ng ml(-1) with good precision and accuracy and the detection limit was down to 0.01 ng ml(-1). The method was found to be relatively selective and was applied successfully to the determination of vanadium in food and hair samples without previous separations. Recovery experiments have also been performed; excellent results were obtained.     

Galvanic stripping determination of trace amounts of lead

A galvanic stripping procedure for rapid determination of trace amounts of lead with a glassy-carbon electrode is described. The method is useful for determining lead at 1-200 ng/ml concentration.     

The radiochemical determination of trace amounts of chloride

Trace amounts of chloride may be determined radiochemically by treating a nonvolatile chloride with a known amount of³⁶Cl labelled hydrochloric acid, evaporating to dryness, and measuring the radioactivity of the residue. In the range 10–100 μg the accuracy is within 3 μg, and in the range of 1–10 μg it is within one microgram. The elimination of certain interferences is demonstrated in the application of the method to one millilitre aliquots of natural water.     

靛蓝胭脂红-溴酸钾体系催化光度法测定微量碘

研究了在室温及0．4mol/L H2SO4介质中碘离子对KBrO3氧化靛蓝胭脂红褪色反应的催化作用,建立了一种测定微量碘的新方法。碘离子浓度在0．20－2．0μg/mL范围内与△A呈线性关系,检测限为0．14μg/mL。多数常见离子无干扰。可用于海带中微量碘的测定。     

催化动力学光度法测定痕量锰

在H2SO4介质中,在表面活性剂壬基酚聚氧乙烯(7)醚的活化下,Mn(Ⅱ)催化溴酸钾氧化甲基紫褪色,建立了动力学光度法测定痕量Mn(Ⅱ)的新方法.考查了最佳试验条件并进行了动力学参数的测定;该方法检出限为2.3×10-7 g/L;线性范围0.0002～0.014 μg/mL;最大相对标准偏差为4.8%.用于水和面粉的测定,回收率在95.0%～104.7%之间;对面粉样用石墨炉原子吸收法进行了对比试验,方法相对误差低于±5.0%.     

Highly sensitive spectrofluorimetric determination of trace amounts of lecithin

A new spectrofluorimetric method was developed for the determination of trace amounts of lecithin using the ciprofloxacin (CIP)–terbium (Tb³⁺) ion complex as a fluorescent probe. In a buffer solution at pH=5.60, lecithin can remarkably reduce the fluorescence intensity of the CIP–Tb³⁺ complex at λ=545 nm. The reduced fluorescence intensity of the Tb³⁺ ion is proportional to the concentration of lecithin. Optimum conditions for the determination of lecithin were also investigated. The linear range and detection limit for the determination of lecithin were 1.0×10⁻⁶–3.0×10⁻⁵ mol L⁻¹ and 3.44×10⁻⁷ mol L⁻¹, respectively. This method is simple, practical, and relatively free of interference from coexisting substances. Furthermore, it has been successfully applied to assess lecithin in serum samples.      

Solid-phase extraction and simultaneous determination of trace amounts of sulphonated and azo sulphonated dyes using microemulsion-modified-zeolite and multivariate calibration

A simple and rapid analytical method for the determination of trace levels of five sulphonated and azo sulphonated reactive dyes: Cibacron Reactive Blue 2 (C-Blue, trisulphonated dye), Cibacron Reactive Red 4 (C-Red, tetrasulphonated azo dye), Cibacron Reactive Yellow 2 (C-Yellow, trisulphonated azo dye), Levafix Brilliant Red E-4BA (L-Red, trisulphonated dye), and Levafix Brilliant Blue E-4BA (L-Blue, disulphonated dye) in water is presented. Initially, the dyes were preconcentrated from 250 ml of water samples with solid-phase extraction using natural zeolite sample previously modified with a microemulsion. The modified zeolite exhibited an excellent extraction for the dyes from solution. The parameters that influence quantitative recovery of reactive dyes like amount of extractant, volume of dye solution, pH, ionic strength, and extraction-elution flow rate were varied and optimized. After elution of the adsorbed dyes, the concentration of dyes was determined spectrophotometrically with the aid of principle component regression (PCR) method without separation of dyes. The results obtained from PCR method were comparable to those obtained from HPLC method confirming the effectiveness of the proposed method. With the aid of SPE by M-zeolite, the concentration of dyes could be reproducibly detected over the range 25-200 ppb for C-Yellow and L-Blue and from 50 to 250 ppb for C-Blue, C-Red, and L-Red. The multivariate detection limits of dyes were found to be 15 ppb for C-Yellow and L-Blue and 25 ppb for C-Blue, C-Red, and L-Red dyes. The proposed chemometric method gave recoveries from 85.4 to 115.3% and R.S.D. from 1.0 to 14.5% for determination of the five dyes without any prior separation for solutes.     

Spectrofluorimetric flow injection determination of trace amounts of periodate

A sensitive, rapid and selective procedure is proposed for the flow injection determinations of periodate by spectrofluorometric detection. The method is based on the reaction of periodate with Alizarin Navy Blue in basic solution. The reagents and manifold variables influence on the sensitivity have been investigated and the optimum conditions are established. Periodate can be determined for the range of 0.250-5.00 microg ml(-1) with a limit of detection of 0.08 microg ml(-1), and with a sample rate of 15 +/- 2 samples h(-1). The relative standard deviations for eight replicate determination of 0.500 and 5.00 microg ml(-1) was 1.3 and 1.1%, respectively. Periodate can be determined in the presence of iodate and bromate. The proposed method was used to determination of periodate in water samples.     

Flow injection spectrophotometric determination of trace amounts of selenium

A simple, rapid and sensitive flow injection spectrophotometric method for determination of selenium (0.005-1.5 mug ml(-1)) is described. The method is based on the catalytic effect of Se(IV) on the reduction reaction of thionine (TN) with sulphide ion, monitored spectrophotometrically at 598 nm. The detection limit is 5 ng ml(-1) the relative standard deviation for eight replicate measurements is 1.1% for 1 mug ml(-1) of selenium. The sampling rate is 25-30 samples h(-1). The procedure was applied successfully to the determination of selenium in real samples.     

Spectrophotometric determination of trace amounts of beryllium in silicate materials

Although photometric determination of beryllium is generally quite satisfactory in trace analysis, application to geochemical samples is restricted because of the numerous interfering ions. Introduction of an extraction procedure eliminates the interference of Al and Fe, which occur in high concentrations in most silicate rocks, and enables beryllium to be determined with Eriochrome Cyanine R. Use of the method for analysis of six international geochemical reference samples containing between 1 and 30 ppm beryllium has given satisfactory results (relative standard deviation from 1.6 to 7.8%).     

Kinetic spectrophotometric determination of trace amounts of selenium and vanadium

A sensitive kinetic spectrophotometric method has been developed for the determination of Se(IV) over the range of 45 to 4000 ng in 10 mL of solution. The method is based on the catalytic effect of Se(IV) on the reduction reaction of bromate by hydrazinium dichloride, with subsequent reaction of Ponceau S with products of the above reaction (chlorine and bromine), causing color changing of Ponceau S. Method development includes optimization of time interval for measurement of slope, pH, reagents concentration, and temperature. The optimized conditions yielded a theoretical detection limit of 33 ng/?10 mL of solution of Se(IV). The interfering effects were studied and removed. The method was applied to the determination of selenium in spiked water, Kjeldahl tablet, selenium tablet, and shampoo. Vanadium(V) has an inhibition effect on the catalyzed reaction of bromate and hydrazine by selenium. Using this effect, V(V) can be determined in the range of 70 to 2500 ng in 10 mL of solution. The optimization procedure includes pH and selenium concentration. An extraction method was used for interference removal. The method was applied to the determination of vanadium in petroleum. Received: 20 October 1998 / Revised: 17 April 1999 / Accepted: 3 June 1999